ICD-10 F99
Billable / SpecificMental disorder, not otherwise specified
About ICD-10-CM F99
ICD-10-CM code F99 represents Mental disorder, not otherwise specified. This is a billable/specific code in the Mental, Behavioral, and Neurodevelopmental chapter (block F99). The 2026 edition of ICD-10-CM F99 became effective on October 1, 2025.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under F99. Per CMS ICD-10-CM Tabular 2026.
- Mental illness NOS
Type 1 Excludes
Pure excludes, these codes can never be coded together with F99. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- unspecified mental disorder due to known physiological condition (F09)
Medicare LCD Coverage for F99
Local Coverage Determinations (LCDs) from CMS MACs that list F99 as a covered diagnosis.
Showing top 10 of 58 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing F99.
1 Cigna
4 Medicare
CPT Codes Commonly Billed with F99
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
We don't have CPT pairings indexed for this specific code yet. Use the CPT search above to find common procedures, or check your payer's published medical policy for code-specific guidance.
Convert F99 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| F99 | 3009 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
ICD-10 F99, Billing FAQ
Is ICD-10 code F99 billable? +
Yes, F99 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to F99? +
ICD-10 F99 includes: Mental illness NOS.
What codes are Type 1 Excludes for F99? +
Type 1 Excludes (never code together with F99): unspecified mental disorder due to known physiological condition (F09)
What ICD-9 codes does F99 map to? +
Per CMS GEMs, F99 maps to ICD-9 codes: 3009. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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